The continuing purpose of this project is to identify domestic animal models applicable to further research into the etiology of cancer in humans. As cases accumulate, it is likely that some types of spontaneous cancers in pet animals can be identified as representing the effects of low-level environmental exposure to carcinogenic agents. The frequency of cancer in these animals would serve as a warning of general environmental hazard(s) to people in the same locale. The topics of current investigation are: 1) environmentally influenced cancer in pet dogs relative to the level and type of industry in their county of residence (e.g., bladder, nasal, and oral cancers); 2) morbidity among pet dogs living in Michigan, potentially exposed to polybrominated biphenyls; 3) morbidity among military working dogs who had considerable exposure to Agent Orange; 4) the epidemiologic features of colorectal cancer, prostatic cancer, and gastrointestinal cancer in pet dogs; and 5) a case-control study of malignant lymphoma in dogs relative to the use of herbicides and pesticides by their owners.